| nanomolar levels of dimethylsulfoniopropionate, dimethylsulfonioacetate, and glycine betaine are sufficient to confer osmoprotection to escherichia coli. | we combined the use of low inoculation titers (300 +/- 100 cfu/ml) and enumeration of culturable cells to measure the osmoprotective potentialities of dimethylsulfoniopropionate (dmsp), dimethylsulfonioacetate (dmsa), and glycine betaine (gb) for salt-stressed cultures of escherichia coli. dilute bacterial cultures were grown with osmoprotectant concentrations that encompassed the nanomolar levels of gb and dmsp found in nature and the millimolar levels of osmoprotectants used in standard labora ... | 1999 | 10427011 |
| is1631 occurrence in bradyrhizobium japonicum highly reiterated sequence-possessing strains with high copy numbers of repeated sequences rsalpha and rsbeta. | from bradyrhizobium japonicum highly reiterated sequence-possessing (hrs) strains indigenous to niigata and tokachi in japan with high copy numbers of the repeated sequences rsalpha and rsbeta (k. minamisawa, t. isawa, y. nakatsuka, and n. ichikawa, appl. environ. microbiol. 64:1845-1851, 1998), several insertion sequence (is)-like elements were isolated by using the formation of dna duplexes by denaturation and renaturation of total dna, followed by treatment with s1 nuclease. most of these seq ... | 1999 | 10427040 |
| colonization pattern of the biocontrol strain pseudomonas chlororaphis ma 342 on barley seeds visualized by using green fluorescent protein. | pseudomonas chlororaphis ma 342 is a potent biocontrol agent that can be used against several seed-borne diseases of cereal crops, including net blotch of barley caused by the fungus drechslera teres. in this study, strain ma 342 was tagged with the gfp gene (encoding the green fluorescent protein) in order to study the fate of cells after seed inoculation. the gfp-tagged strain, ma 342g2, had the same biocontrol efficacy as the wild type when it was applied at high cell concentrations to seeds ... | 1999 | 10427065 |
| the viable-but-nonculturable condition is induced by copper in agrobacterium tumefaciens and rhizobium leguminosarum. | many bacteria respond to changes in environmental conditions by entering the viable-but-nonculturable state. we have determined that copper can induce nutrient-starved agrobacterium tumefaciens and rhizobium leguminosarum cells to become viable but nonculturable. this is the first report of a chemical inducer of this condition. | 1999 | 10427081 |
| genome signature comparisons among prokaryote, plasmid, and mitochondrial dna. | our basic observation is that each genome has a characteristic "signature" defined as the ratios between the observed dinucleotide frequencies and the frequencies expected if neighbors were chosen at random (dinucleotide relative abundances). the remarkable fact is that the signature is relatively constant throughout the genome; i.e. , the patterns and levels of dinucleotide relative abundances of every 50-kb segment of the genome are about the same. comparison of the signatures of different gen ... | 1999 | 10430917 |
| a chimeric prokaryotic ancestry of mitochondria and primitive eukaryotes. | we provide data and analysis to support the hypothesis that the ancestor of animal mitochondria (mt) and many primitive amitochondrial (a-mt) eukaryotes was a fusion microbe composed of a clostridium-like eubacterium and a sulfolobus-like archaebacterium. the analysis is based on several observations: (i) the genome signatures (dinucleotide relative abundance values) of clostridium and sulfolobus are compatible (sufficiently similar) and each has significantly more similarity in genome signature ... | 1999 | 10430918 |
| a high-density physical map of sinorhizobium meliloti 1021 chromosome derived from bacterial artificial chromosome library. | as part of the european sinorhizobium meliloti (strain 1021) chromosome sequencing project, four genomic bacterial artificial chromosome (bac) libraries have been constructed, one of which was mainly used for chromosome mapping. this library consists of 1,824 clones with an average insert size of 80 kilobases and represents approximately 20-fold total genome coverage [6.8 megabases (mbs)]. pcr screening of 384 bac clones with 447 chromosomal markers (pcr primer pairs), consisting of 73 markers r ... | 1999 | 10430947 |
| expression of a serratia marcescens chitinase gene in sinorhizobium fredii usda191 and sinorhizobium meliloti rcr2011 impedes soybean and alfalfa nodulation. | a gene encoding chitinase from serratia marcescens bjl200 was cloned into a broad-host-range vector (prk415) and mobilized into sinorhizobium fredii usda191. chitinolytic activity was detected in s. fredii usda191 transconjugants that carried the s. marcescens chib gene. chitinase-producing s. fredii usda191 formed nodules on soybean cultivar mccall. however, there was a delay in nodule formation and a marked decrease in the total number of nodules formed by the chitinase-producing s. fredii in ... | 1999 | 10432638 |
| transformations in flagellar structure of rhodobacter sphaeroides and possible relationship to changes in swimming speed. | rhodobacter sphaeroides is a photosynthetic bacterium which swims by rotating a single flagellum in one direction, periodically stopping, and reorienting during these stops. free-swimming r. sphaeroides was examined by both differential interference contrast (dic) microscopy, which allows the flagella of swimming cells to be seen in vivo, and tracking microscopy, which tracks swimming patterns in three dimensions. dic microscopy showed that when rotation stopped, the helical flagellum relaxed in ... | 1999 | 10438751 |
| regulation of the lic operon of bacillus subtilis and characterization of potential phosphorylation sites of the licr regulator protein by site-directed mutagenesis. | the lic operon of bacillus subtilis is required for the transport and degradation of oligomeric beta-glucosides, which are produced by extracellular enzymes on substrates such as lichenan or barley glucan. the lic operon is transcribed from a sigma(a)-dependent promoter and is inducible by lichenan, lichenan hydrolysate, and cellobiose. induction of the operon requires a dna sequence with dyad symmetry located immediately upstream of the licbcah promoter. expression of the lic operon is positive ... | 1999 | 10438772 |
| the bvr locus of listeria monocytogenes mediates virulence gene repression by beta-glucosides. | the beta-glucoside cellobiose has been reported to specifically repress the prfa-dependent virulence genes hly and plca in listeria monocytogenes nctc 7973. this led to the hypothesis that beta-glucosides, sugars of plant origin, may act as signal molecules, preventing the expression of virulence genes if l. monocytogenes is living in its natural habitat (soil). in three other laboratory strains (egd, l028, and 10403s), however, the effect of cellobiose was not unique, and all fermentable carboh ... | 1999 | 10438775 |
| conserved cytoplasmic loops are important for both the transport and chemotaxis functions of pcak, a protein from pseudomonas putida with 12 membrane-spanning regions. | chemotaxis to the aromatic acid 4-hydroxybenzoate (4-hba) by pseudomonas putida is mediated by pcak, a membrane-bound protein that also functions as a 4-hba transporter. pcak belongs to the major facilitator superfamily (mfs) of transport proteins, none of which have so far been implicated in chemotaxis. work with two well-studied mfs transporters, lacy (the lactose permease) and teta (a tetracycline efflux protein), has revealed two stretches of amino acids located between the second and third ... | 1999 | 10438780 |
| survival and exopolysaccharide production in sinorhizobium meliloti wsm419 are affected by calcium and low ph. | cells of sinorhizobium meliloti wsm419 showed an adaptive acid-tolerance response when grown at ph 5.8 instead of ph 7.0. increasing concentrations of calcium in the exposure medium significantly decreased the death rate of wsm419 cells under conditions of acid stress (ph 4.0). the effect of calcium on survival at ph 4.0 however, appears unconnected to exopolysaccharide (eps), since a strain with a mutation in exoy (rm0540) responded to calcium in the exposure medium in the same way as its wild- ... | 1999 | 10439397 |
| bacterial dna methylation: a cell cycle regulator? | | 1999 | 10464180 |
| combined genetic and physical map of the complex genome of agrobacterium tumefaciens. | a combined genetic and physical map of the agrobacterium tumefaciens a348 (derivative of c58) genome was constructed to address the discrepancy between initial single-chromosome genetic maps and more recent physical mapping data supporting the presence of two nonhomologous chromosomes. the combined map confirms the two-chromosome genomic structure and the correspondence of the initial genetic maps to the circular chromosome. the linear chromosome is almost devoid of auxotrophic markers, which pr ... | 1999 | 10464183 |
| molecular characterization of type-specific capsular polysaccharide biosynthesis genes of streptococcus agalactiae type ia. | the type-specific capsular polysaccharide (cp) of a group b streptococcus, streptococcus agalactiae type ia, is a high-molecular-weight polymer consisting of the pentasaccharide repeating unit 4)-[alpha-d-neupnac-(2-->3)-beta-d-galp-(1-->4)-beta-d-glcpnac-(1- ->3 )]-beta-d-galp-(1-->4)-beta-d-glcp-(1. here, cloning, sequencing, and transcription of the type ia-specific capsular polysaccharide synthesis (cps) genes and functional analysis of these gene products are described. a 26-kb dna fragment ... | 1999 | 10464185 |
| reduction of adenosine-5'-phosphosulfate instead of 3'-phosphoadenosine-5'-phosphosulfate in cysteine biosynthesis by rhizobium meliloti and other members of the family rhizobiaceae. | we have cloned and sequenced three genes from rhizobium meliloti (sinorhizobium meliloti) that are involved in sulfate activation for cysteine biosynthesis. two of the genes display homology to the escherichia coli cysdn genes, which code for an atp sulfurylase (ec 2.7.7.4). the third gene has homology to the e. coli cysh gene, a 3'-phosphoadenosine-5'-phosphosulfate (paps) reductase (ec 1.8.99.4), but has greater homology to a set of genes found in arabidopsis thaliana that encode an adenosine- ... | 1999 | 10464198 |
| mutations affecting motifs of unknown function in the central domain of nitrogen regulatory protein c. | the positive control function of the bacterial enhancer-binding protein ntrc resides in its central domain, which is highly conserved among activators of sigma54 holoenzyme. previous studies of a small set of mutant forms specifically defective in transcriptional activation, called ntrc repressor [ntrc(rep)] proteins, had enabled us to locate various functional determinants in the central domain. in this more comprehensive survey, the dna encoding a major portion of the central domain was random ... | 1999 | 10464219 |
| characterization of a pseudomonas aeruginosa fatty acid biosynthetic gene cluster: purification of acyl carrier protein (acp) and malonyl-coenzyme a:acp transacylase (fabd). | a dna fragment containing the pseudomonas aeruginosa fabd (encoding malonyl-coenzyme a [coa]:acyl carrier protein [acp] transacylase), fabg (encoding beta-ketoacyl-acp reductase), acpp (encoding acp), and fabf (encoding beta-ketoacyl-acp synthase ii) genes was cloned and sequenced. this fab gene cluster is delimited by the plsx (encoding a poorly understood enzyme of phospholipid metabolism) and pabc (encoding 4-amino-4-deoxychorismate lyase) genes; the fabf and pabc genes seem to be translation ... | 1999 | 10464226 |
| molecular and biochemical characterization of two xylanase-encoding genes from cellulomonas pachnodae. | two xylanase-encoding genes, named xyn11a and xyn10b, were isolated from a genomic library of cellulomonas pachnodae by expression in escherichia coli. the deduced polypeptide, xyn11a, consists of 335 amino acids with a calculated molecular mass of 34,383 da. different domains could be identified in the xyn11a protein on the basis of homology searches. xyn11a contains a catalytic domain belonging to family 11 glycosyl hydrolases and a c-terminal xylan binding domain, which are separated from the ... | 1999 | 10473422 |
| development and application of pathovar-specific monoclonal antibodies that recognize the lipopolysaccharide o antigen and the type iv fimbriae of xanthomonas hyacinthi. | the objective of this study was to develop a specific immunological diagnostic assay for yellow disease in hyacinths, using monoclonal antibodies (mabs). mice were immunized with a crude cell wall preparation (shear fraction) from xanthomonas hyacinthi and with purified type iv fimbriae. hybridomas were screened for a positive reaction with x. hyacinthi cells or fimbriae and for a negative reaction with x. translucens pv. graminis or erwinia carotovora subsp. carotovora. nine mabs recognized fim ... | 1999 | 10473431 |
| identification of nodulation promoter (nod-box) regions of rhizobium galegae. | a hybridisation analysis of a genomic clone library of rhizobium galegae hambi 1174 located four ecori fragments homologous to the nod-box promoter sequence of sinorhizobium meliloti in two separate gene regions. two of the five nod-boxes detected in the r. galegae genome were carried on a single cosmid clone, prg30, upstream from the nodabcij and nodf genes, whereas the other three nod-boxes were carried on a different cosmid clone, prg10. hybridisations with various nod gene probes from s. mel ... | 1999 | 10474187 |
| gliding motility in bacteria: insights from studies of myxococcus xanthus. | gliding motility is observed in a large variety of phylogenetically unrelated bacteria. gliding provides a means for microbes to travel in environments with a low water content, such as might be found in biofilms, microbial mats, and soil. gliding is defined as the movement of a cell on a surface in the direction of the long axis of the cell. because this definition is operational and not mechanistic, the underlying molecular motor(s) may be quite different in diverse microbes. in fact, studies ... | 1999 | 10477310 |
| hp0333, a member of the dpra family, is involved in natural transformation in helicobacter pylori. | helicobacter pylori is naturally competent for dna transformation, but the mechanism by which transformation occurs is not known. for haemophilus influenzae, dpra is required for transformation by chromosomal but not plasmid dna, and the complete genomic sequence of h. pylori 26695 revealed a dpra homolog (hp0333). examination of genetic databases indicates that dpra homologs are present in a wide variety of bacterial species. to examine whether hp0333 has a function similar to dpra of h. influe ... | 1999 | 10482496 |
| identification of a plasmid-borne locus in rhizobium etli kim5s involved in lipopolysaccharide o-chain biosynthesis and nodulation of phaseolus vulgaris. | screening of derivatives of rhizobium etli kim5s randomly mutagenized with mtn5ssgusa30 resulted in the identification of strain kim-g1. its rough colony appearance, flocculation in liquid culture, and ndv(-) fix(-) phenotype were indicative of a lipopolysaccharide (lps) defect. electrophoretic analysis of cell-associated polysaccharides showed that kim-g1 produces only rough lps. composition analysis of purified lps oligosaccharides from kim-g1 indicated that it produces an intact lps core tris ... | 1999 | 10482500 |
| inactivation and regulation of the aerobic c(4)-dicarboxylate transport (dcta) gene of escherichia coli. | the gene (dcta) encoding the aerobic c(4)-dicarboxylate transporter (dcta) of escherichia coli was previously mapped to the 79-min region of the linkage map. the nucleotide sequence of this region reveals two candidates for the dcta gene: f428 at 79.3 min and the o157a-o424-o328 (or orfqmp) operon at 79.9 min. the f428 gene encodes a homologue of the sinorhizobium meliloti and rhizobium leguminosarum h(+)/c(4)-dicarboxylate symporter, dcta, whereas the orfqmp operon encodes homologues of the aer ... | 1999 | 10482502 |
| involvement of the cis/trans isomerase cti in solvent resistance of pseudomonas putida dot-t1e. | pseudomonas putida dot-t1e is a solvent-resistant strain that is able to grow in the presence of high concentrations of toluene. we have cloned and sequenced the cti gene of this strain, which encodes the cis/trans isomerase, termed cti, that catalyzes the cis-trans isomerization of esterified fatty acids in phospholipids, mainly cis-oleic acid (c(16:1,9)) and cis-vaccenic acid (c(18:1,11)), in response to solvents. to determine the importance of this cis/trans isomerase for solvent resistance a ... | 1999 | 10482510 |
| flavan-containing cells delimit frankia-infected compartments in casuarina glauca nodules. | we investigated the involvement of polyphenols in the casuarina glauca-frankia symbiosis. histological analysis revealed a cell-specific accumulation of phenolics in c. glauca nodule lobes, creating a compartmentation in the cortex. histochemical and biochemical analyses indicated that these phenolic compounds belong to the flavan class of flavonoids. we show that the same compounds were synthesized in nodules and uninfected roots. however, the amount of each flavan was dramatically increased in ... | 1999 | 10482666 |
| the eff-482 locus of sinorhizobium meliloti cxm1-105 that influences symbiotic effectiveness consists of three genes encoding an endoglycanase, a transcriptional regulator and an adenylate cyclase. | the mutant t482 of sinorhizobium meliloti cxm1-105, which carries a tn5 insertion on megaplasmid 1, exhibits an enhanced symbiotic efficiency phenotype. three genes, eglc, cya3 and syrb2, were identified in the eff-482 region tagged by the tn5 insertion in t482. the eglc gene encodes an endoglycanase which contributes to the depolymerization of the exo-polysaccharide succinoglycan. the n-terminal region of the predicted cya3 gene product was similar to eukaryotic-type adenylate cyclases from bre ... | 1999 | 10485295 |
| the sinorhizobium meliloti insertion sequence (is) element isrm14 is related to a previously unrecognized is element located adjacent to the escherichia coli locus of enterocyte effacement (lee) pathogenicity island. | isrm14 is 2695 basepairs (bp) in size and bordered by 22 bp imperfect inverted repeats (irs). a 9-bp target sequence is duplicated upon isrm14 transposition. the dna strand that putatively encodes the transposase enzyme carries three open reading frames (orfs) designated orfs1 to 3, which specify putative proteins of 15. 9 kda, 13.1 kda, and 61.1 kda, respectively. according to its structural characteristics, isrm14 belongs to the recently proposed is66 family of is elements. the orfs1 to 3 enco ... | 1999 | 10489437 |
| cyclic organization of the carbohydrate metabolism in sinorhizobium meliloti. | the pathways of polysaccharide biosynthesis were investigated in cells of sinorhizobium meliloti (strain su47) using a stable isotope approach. the isotopic labeling of the periplasmic beta-1,2-glucans synthesized from glucose labeled at various positions evidenced the involvement of catabolic pathways, namely the pentose-phosphate and entner-doudoroff pathways, into the early steps of polysaccharide synthesis. the exopolysaccharides produced at the same time had a labeling pattern similar to th ... | 1999 | 10491206 |
| bios, a biotin-induced, stationary-phase, and possible lysr-type regulator in sinorhizobium meliloti. | sinorhizobium meliloti 1021 produces biotin required for growth, but it also responds to external biotin signals from alfalfa plants through the bios regulatory locus. mutation of bios increases biotin uptake, extends stationary phase in the presence of biotin, and impairs competitive growth in the presence of biotin. new data supporting the relevance of this gene to plant-microbe interactions show that a bios-gusa reporter fusion is expressed by bacteria on plant roots, by bacteria in alfalfa r ... | 1999 | 10494632 |
| nitrite and nitrous oxide reductase regulation by nitrogen oxides in rhodobacter sphaeroides f. sp. denitrificans il106. | we have cloned the nap locus encoding the periplasmic nitrate reductase in rhodobacter sphaeroides f. sp. denitrificans il106. a mutant with this enzyme deleted is unable to grow under denitrifying conditions. biochemical analysis of this mutant shows that in contrast to the wild-type strain, the level of synthesis of the nitrite and n(2)o reductases is not increased by the addition of nitrate. growth under denitrifying conditions and induction of n oxide reductase synthesis are both restored by ... | 1999 | 10498715 |
| flbt couples flagellum assembly to gene expression in caulobacter crescentus. | the biogenesis of the polar flagellum of caulobacter crescentus is regulated by the cell cycle as well as by a trans-acting regulatory hierarchy that functions to couple flagellum assembly to gene expression. the assembly of early flagellar structures (ms ring, switch, and flagellum-specific secretory system) is required for the transcription of class iii genes, which encode the remainder of the basal body and the external hook structure. similarly, the assembly of class iii gene-encoded structu ... | 1999 | 10498731 |
| regulation of divergent transcription from the uvra-ssb promoters in sinorhizobium meliloti. | the sinorhizobium meliloti uvra gene was isolated by complementation of a rhodobacter sphaeroides uvra- mutant. dna sequencing of the region upstream of the s. meliloti uvra gene reveals the presence of the ssb gene in the opposite transcriptional orientation. pcr-mediated mutagenesis demonstrated that expression of these two genes is inducible by dna damage, and depends, in both cases, on the direct repeat gttcn7gttc (cited according to the direction of uvra transcription). comparison of the se ... | 1999 | 10503543 |
| utilization of trihalogenated propanes by agrobacterium radiobacter ad1 through heterologous expression of the haloalkane dehalogenase from rhodococcus sp. strain m15-3. | trihalogenated propanes are toxic and recalcitrant organic compounds. attempts to obtain pure bacterial cultures able to use these compounds as sole carbon and energy sources were unsuccessful. both the haloalkane dehalogenase from xanthobacter autotrophicus gj10 (dhla) and that from rhodococcus sp. strain m15-3 (dhaa) were found to dehalogenate trihalopropanes to 2,3-dihalogenated propanols, but the kinetic properties of the latter enzyme are much better. broad-host-range dehalogenase expressio ... | 1999 | 10508091 |
| fate of plasmid-bearing, luciferase marker gene tagged bacteria after feeding to the soil microarthropod onychiurus fimatus (collembola). | in order to study the potential impact of the soil microarthropod onychiurus fimatus (collembola) on the microbial community, we analysed the fate of luciferase marker gene tagged bacterial strains fed to young adult specimens in petri dish microcosm experiments. in faeces collected from o. fimatus, escherichia coli s17-1/prp4luc and sinorhizobium meliloti l33 were only detectable for 2 days after feeding whereas strain hr2/prp4luc, a close relative of stenotrophomonas maltophilia, isolated from ... | 1999 | 10508937 |
| unraveling the function of glycosyltransferases in streptococcus thermophilus sfi6. | streptococcus thermophilus sfi6 produces a texturizing exopolysaccharide (eps) consisting of a -->3)[alpha-d-galp-(1-->6)]-beta-d-glcp-(1-->3)-alpha-d-galpnac-(1--> 3)-beta-d-galp-(1--> repeating unit. we previously identified and analyzed a 14.5-kb gene cluster from s. thermophilus sfi6 consisting of 13 genes responsible for its eps production. within this gene cluster, we found a central region of genes (epse, epsf, epsg, and epsi) that showed similarity to glycosyltransferases. in this study, ... | 1999 | 10515925 |
| influence of fermentation conditions and microfiltration processes on membrane fouling during recovery of glucuronane polysaccharides from fermentation broths. | we have investigated the recovery of exopolysaccharides produced by sinorhizobium meliloti m5n1 cs bacteria from fermentation broths using different membrane filtration processes: cross-flow filtration with a 7 mm i.d. tubular ceramic membrane of 0.5-microm pores under fixed transmembrane pressure or fixed permeate flux and dynamic filtration with a 0.2 microm nylon membrane using a 16-cm rotating disc filter. with the tubular membrane, the polysaccharide mass flux was mainly limited by polymer ... | 1999 | 10516575 |
| the upstream region of the nodd3 gene of sinorhizobium meliloti carries enhancer sequences for the transcriptional activator ntrc. | in sinorhizobium meliloti the expression of the nodulation genes nodabc is regulated in response to the level of fixed nitrogen (ammonia). previous results suggested that the response to the nitrogen status is mediated by the two-component ntrb/ntrc system which controls transcription of the nodd3 gene, encoding a positive regulatory protein for the activation of nodabc transcription. here we confirm by dnase i footprinting and gel shift assays that ntrc, when phosphorylated by ntrb, is able to ... | 1999 | 10518756 |
| alteration of enod40 expression modifies medicago truncatula root nodule development induced by sinorhizobium meliloti | molecular mechanisms involved in the control of root nodule organogenesis in the plant host are poorly understood. one of the nodulin genes associated with the earliest phases of this developmental program is enod40. we show here that transgenic medicago truncatula plants overexpressing enod40 exhibit accelerated nodulation induced by sinorhizobium meliloti. this resulted from increased initiation of primordia, which was accompanied by a proliferation response of the region close to the root tip ... | 1999 | 10521525 |
| biosynthesis of trehalose from maltooligosaccharides in rhizobia. | previously, the enzymes for trehalose synthesis that are present in escherichia coli were demonstrated in bradyrhizobium japonicum and b. elkanii. an alternative mechanism recently reported for the synthesis of trehalose from maltooligosaccharides was considered based on the fact that high concentrations of sugars in liquid culture stimulated the accumulation of trehalose. an assay for the synthesis of trehalose from maltooligosaccharides using crude, gel-filtered protein preparations was develo ... | 1999 | 10528404 |
| identification of regions of the chromosome of neisseria meningitidis and neisseria gonorrhoeae which are specific to the pathogenic neisseria species. | neisseria meningitidis and neisseria gonorrhoeae give rise to dramatically different diseases. their interactions with the host, however, do share common characteristics: they are both human pathogens which do not survive in the environment and which colonize and invade mucosa at their port of entry. it is therefore likely that they have common properties that might not be found in nonpathogenic bacteria belonging to the same genetically related group, such as neisseria lactamica. their common p ... | 1999 | 10531275 |
| identification of lumichrome as a sinorhizobium enhancer of alfalfa root respiration and shoot growth. | sinorhizobium meliloti bacteria produce a signal molecule that enhances root respiration in alfalfa (medicago sativa l.) and also triggers a compensatory increase in whole-plant net carbon assimilation. nuclear magnetic resonance, mass spectrometry, and ultraviolet-visible absorption identify the enhancer as lumichrome, a common breakdown product of riboflavin. treating alfalfa roots with 3 nm lumichrome increased root respiration 21% (p < 0.05) within 48 h. a closely linked increase in net carb ... | 1999 | 10535912 |
| a protein residing at the subunit interface of the bacterial ribosome. | surface labeling of escherichia coli ribosomes with the use of the tritium bombardment technique has revealed a minor unidentified ribosome-bound protein (spot y) that is hidden in the 70s ribosome and becomes highly labeled on dissociation of the 70s ribosome into subunits. in the present work, the n-terminal sequence of the protein y was determined and its gene was identified as yfia, an orf located upstream the phe operon of e. coli. this 12.7-kda protein was isolated and characterized. an af ... | 1999 | 10535924 |
| transcription regulation of the nir gene cluster encoding nitrite reductase of paracoccus denitrificans involves nnr and niri, a novel type of membrane protein. | the nirix gene cluster of paracoccus denitrificans is located between the nir and nor gene clusters encoding nitrite and nitric oxide reductases respectively. the niri sequence corresponds to that of a membrane-bound protein with six transmembrane helices, a large periplasmic domain and cysteine-rich cytoplasmic domains that resemble the binding sites of [4fe-4s] clusters in many ferredoxin-like proteins. nirx is soluble and apparently located in the periplasm, as judged by the predicted signal ... | 1999 | 10540283 |
| on the origin of branches in escherichia coli. | some escherichia coli strains with impaired cell division form branched cells at high frequencies during certain growth conditions. here, we show that neither ftsi nor ftsz activity is required for the development of branches. buds did not form at specific positions along the cell surface during high-branching conditions. antibiotics affecting cell wall synthesis had a positive effect on branch formation in the case of ampicillin, cephalexin, and penicillin g, whereas mecillinam and d-cycloserin ... | 1999 | 10542160 |
| the cpxra signal transduction system of escherichia coli: growth-related autoactivation and control of unanticipated target operons. | in escherichia coli, the cpxra two-component signal transduction system senses and responds to aggregated and misfolded proteins in the bacterial envelope. we show that cpxr-p (the phosphorylated form of the cognate response regulator) activates cpxra expression in conjunction with rpos, suggesting an involvement of the cpx system in stationary-phase survival. engagement of the cpxra system in functions beyond protein management is indicated by several putative targets identified after a genomic ... | 1999 | 10542180 |
| structural characterization of the symbiotically important low-molecular-weight succinoglycan of sinorhizobium meliloti. | the production of succinoglycan by sinorhizobium meliloti rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. low-molecular-weight (lmw) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been rep ... | 1999 | 10542182 |
| inhibition of the fixl sensor kinase by the fixt protein in sinorhizobium meliloti. | nitrogen fixation in symbiotic rhizobia is subject to multiple levels of gene regulation. in sinorhizobium meliloti, the alfalfa symbiont, the fixlj two-component regulatory system plays a major role in inducing nitrogen fixation and respiration gene expression in response to the low ambient o(2) concentration of the nodule. here we report on the mode of action of the fixt protein, a recently identified repressor of nitrogen fixation gene expression in s. meliloti. first, we provide evidence tha ... | 1999 | 10542296 |
| isolation of polymyxin b-susceptible mutants of burkholderia pseudomallei and molecular characterization of genetic loci involved in polymyxin b resistance. | burkholderia pseudomallei is a gram-negative bacterium that causes the disease known as melioidosis. this pathogen is endemic to southeast asia and northern australia and is particularly problematic in northeastern thailand. it has been previously reported that b. pseudomallei is resistant to the killing action of cationic antimicrobial peptides, including human neutrophil peptide, protamine sulfate, poly-l-lysine, magainins, and polymyxins. recently, we have also found that the virulent clinica ... | 1999 | 10543742 |
| characterization of an operon encoding two c-type cytochromes, an aa(3)-type cytochrome oxidase, and rusticyanin in thiobacillus ferrooxidans atcc 33020. | despite the importance of thiobacillus ferrooxidans in bioremediation and bioleaching, little is known about the genes encoding electron transfer proteins implicated in its energetic metabolism. this paper reports the sequences of the four cox genes encoding the subunits of an aa(3)-type cytochrome c oxidase. these genes are in a locus containing four other genes: cyc2, which encodes a high-molecular-weight cytochrome c; cyc1, which encodes a c(4)-type cytochrome (c(552)); open reading frame 1, ... | 1999 | 10543786 |
| methanotroph diversity in landfill soil: isolation of novel type i and type ii methanotrophs whose presence was suggested by culture-independent 16s ribosomal dna analysis. | the diversity of the methanotrophic community in mildly acidic landfill cover soil was assessed by three methods: two culture-independent molecular approaches and a traditional culture-based approach. for the first of the molecular studies, two primer pairs specific for the 16s rrna gene of validly published type i (including the former type x) and type ii methanotrophs were identified and tested. these primers were used to amplify directly extracted soil dna, and the products were used to const ... | 1999 | 10543800 |
| epitope identification for a panel of anti-sinorhizobium meliloti monoclonal antibodies and application to the analysis of k antigens and lipopolysaccharides from bacteroids. | in two published reports using monoclonal antibodies (mabs) generated against whole cells, olsen et al. showed that strain-specific antigens on the surface of cultured cells of sinorhizobium meliloti were diminished or absent in the endophytic cells (bacteroids) recovered from alfalfa nodules, whereas two common antigens were not affected by bacterial differentiation (p. olsen, m. collins, and w. rice, can. j. microbiol. 38:506-509, 1992; p. olsen, s. wright, m. collins, and w. rice, appl. envir ... | 1999 | 10543844 |
| glutathione and homoglutathione synthesis in legume root nodules. | high-performance liquid chromatography (hplc) with fluorescence detection was used to study thiol metabolism in legume nodules. glutathione (gsh) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (vigna unguiculata), whereas homoglutathione (hgsh) predominated in soybean (glycine max), bean (phaseolus vulgaris), and mungbean (vigna radiata) nodules. all nodules had greater thiol concentrations than the leaves and roots of the s ... | 1999 | 10557236 |
| characterization of a periplasmic atp-binding cassette iron import system of brachyspira (serpulina) hyodysenteriae. | the nucleotide sequence of the pathogenic spirochete brachyspira hyodysenteriae bit (for "brachyspira iron transport") genomic region has been determined. the bit region is likely to encode an iron atp-binding cassette transport system with some homology to those encountered in gram-negative bacteria. six open reading frames oriented in the same direction and physically linked have been identified. this system possesses a protein containing atp-binding motifs (bitd), two hydrophobic cytoplasmic ... | 1999 | 10559160 |
| role of ccpa in regulation of the central pathways of carbon catabolism in bacillus subtilis. | the bacillus subtilis two-dimensional (2d) protein index contains almost all glycolytic and tricarboxylic acid (tca) cycle enzymes, among them the most abundant housekeeping proteins of growing cells. therefore, a comprehensive study on the regulation of glycolysis and the tca cycle was initiated. whereas expression of genes encoding the upper and lower parts of glycolysis (pgi, pfk, fbaa, and pyka) is not affected by the glucose supply, there is an activation of the glycolytic gap gene and the ... | 1999 | 10559165 |
| phosphorylation-induced dimerization of the fixj receiver domain. | the 'two-component' transcriptional activator fixj controls nitrogen fixation in sinorhizobium meliloti. phosphorylation of fixj induces its dimerization, as evidenced by gel permeation chromatography and equilibrium sedimentation analysis. phosphorylation-induced dimerization is an intrinsic property of the isolated receiver domain fixjn. accordingly, chemical phosphorylation of both fixj and fixjn are second-order reactions with respect to protein concentration. however, the second-order phosp ... | 1999 | 10564492 |
| isrm10: a new insertion sequence of sinorhizobium meliloti: nucleotide sequence and geographic distribution. | in this study the description of a new insertion sequence of sinorhizobium meliloti, isrm10, is reported. isrm10 was found in the intergenic region between nodj and nodq of a natural isolated strain. isrm10 was 1047 bp long and showed the typical features of the iss belonging to the is630-tc1/is3 superfamily. in particular the isrm10 nucleotide sequence showed the highest homology (62%) with a sphingomonas aromaticivorans is. isrm10 was present in 32% of the analyzed s. meliloti strains while it ... | 1999 | 10564804 |
| a rhizobial homolog of ihf stimulates transcription of dcta in rhizobium leguminosarum but not in sinorhizobium meliloti. | sequence inspection identified several potential ihf binding sites adjacent to the rhizobium leguminosarum dcta promoter. ihf protected the -30 to -76 region from dnase i digestion, but systematic error in quantitative assays suggested that this protein dna interaction is complex. ihf stimulated dctd-mediated transcriptional activation from the r. leguminosarum dcta promoter both in vivo and in vitro. in contrast to r. leguminosarum dcta, the sinorhizobium meliloti dcta promoter region was found ... | 1999 | 10570977 |
| characterization of the bradyrhizobium japonicum ftsh gene and its product. | the bradyrhizobium japonicum ftsh gene was cloned by using a set of widely applicable degenerated oligonucleotides. western blot experiments indicated that the ftsh protein was produced under standard growth conditions and that it was not heat inducible. attempts to delete the ftsh gene in b. japonicum failed, suggesting a pivotal cellular function of this gene. the expression of b. japonicum ftsh in an ftsh-negative escherichia coli strain significantly enhanced the fitness of this mutant and r ... | 1999 | 10572147 |
| osmoprotection of escherichia coli by peptone is mediated by the uptake and accumulation of free proline but not of proline-containing peptides. | the effect of meat peptone type i (sigma) on the growth of escherichia coli cells under hyperosmotic stress has been investigated. peptone is a complex mixture of peptides with a small content of free amino acids, which resembles nutrients found in natural environments. our data showed that peptone enhances the growth of e. coli cells in high-osmolarity medium to levels higher than those achieved with the main compatible solute in bacteria, glycine betaine. the mechanism of osmoprotection by pep ... | 1999 | 10583976 |
| rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate. | biological n(2) fixation represents the major source of n input in agricultural soils including those in arid regions. the major n(2)-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-n soils. the rhizobium-legume symbioses have received most attention and have been examined extensively. the behavior of some n(2)-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinit ... | 1999 | 10585971 |
| alfalfa and tobacco cells react differently to chitin oligosaccharides and sinorhizobium meliloti nodulation factors | alfalfa (medicago sativa l.) suspension cultures respond to yeast elicitors with a strong alkalinization of the culture medium, a transient synthesis of activated oxygen species, and typical late defence reactions such as phytoalexin accumulation and increased peroxidase activity. the alkalinization reaction as well as the oxidative burst were also observed when tobacco (nicotiana tabacum l. ) cell-suspension cultures were treated with yeast elicitors. depending on the degree of polymerization, ... | 1999 | 10592044 |
| non-coding, mrna-like rnas database y2k. | in last few years much data has accumulated on various non-translatable rna transcripts that are synthesised in different cells. they are lacking in protein coding capacity and it seems that they work mainly or exclusively at the rna level. all known non-coding rna transcripts are collected in the database: http://www. man.poznan.pl/5sdata/ncrna/index.html | 2000 | 10592224 |
| genetic and functional analyses of the conserved c-terminal core domain of escherichia coli ftsz. | in escherichia coli, ftsz is required for the recruitment of the essential cell division proteins ftsa and zipa to the septal ring. several c-terminal deletions of e. coli ftsz, including one of only 12 amino acids that removes the highly conserved c-terminal core domain, failed to complement chromosomal ftsz mutants when expressed on a plasmid. to identify key individual residues within the core domain, six highly conserved residues were replaced with alanines. all but one of these mutants (d37 ... | 1999 | 10601211 |
| citrate synthase mutants of sinorhizobium meliloti are ineffective and have altered cell surface polysaccharides. | the glta gene, encoding sinorhizobium meliloti 104a14 citrate synthase, was isolated by complementing an escherichia coli glta mutant. the s. meliloti glta gene was mutated by inserting a kanamycin resistance gene and then using homologous recombination to replace the wild-type glta with the glta::kan allele. the resulting strain, csdx1, was a glutamate auxotroph, and enzyme assays confirmed the absence of a requirement for glutamate. csdx1 did not grow on succinate, malate, aspartate, pyruvate, ... | 1999 | 10601220 |
| sinorhizobium meliloti strain 1021 bios and bdha gene transcriptions are both affected by biotin available in defined medium. | sinorhizobium meliloti 1021 responds to external biotin signals from alfalfa plants through the bios regulatory locus. immunogold labeling and electron microscopy revealed that the bios protein is located within the s. meliloti cytoplasm. under biotin-limiting conditions the s. meliloti cell lumen was filled with polyhydroxybutyrate (phb) granules suggesting that either phb synthesis or degradation are influenced by biotin. to test this hypothesis a 3-hydroxybutyrate-dehydrogenase-lacz (bdha-lac ... | 2000 | 10612728 |
| proline catabolism by pseudomonas putida: cloning, characterization, and expression of the put genes in the presence of root exudates. | pseudomonas putida kt2442 is a root-colonizing strain which can use proline, one of the major components in root exudates, as its sole carbon and nitrogen source. a p. putida mutant unable to grow with proline as the sole carbon and nitrogen source was isolated after random mini-tn5-km mutagenesis. the mini-tn5 insertion was located at the puta gene, which is adjacent to and divergent from the putp gene. the puta gene codes for a protein of 1,315 amino acid residues which is homologous to the pu ... | 2000 | 10613867 |
| hbar, a 4-hydroxybenzoate sensor and fnr-crp superfamily member, regulates anaerobic 4-hydroxybenzoate degradation by rhodopseudomonas palustris. | under anaerobic conditions, structurally diverse aromatic compounds are catabolized by bacteria to form benzoyl-coenzyme a (benzoyl-coa), the starting compound for a central reductive pathway for aromatic ring degradation. the structural genes required for the conversion of 4-hydroxybenzoate (4-hba) to benzoyl-coa by rhodopseudomonas palustris have been identified. here we describe a regulatory gene, hbar, that is part of the 4-hba degradation gene cluster. an hbar mutant that was constructed wa ... | 2000 | 10613868 |
| identification of a new class of 5'-adenylylsulfate (aps) reductases from sulfate-assimilating bacteria. | a gene was cloned from burkholderia cepacia dbo1 that is homologous with escherichia coli cysh encoding 3'-phosphoadenylylsulfate (paps) reductase. the b. cepacia gene is the most recent addition to a growing list of cysh homologs from a diverse group of sulfate-assimilating bacteria whose products show greater homology to plant 5'-adenylylsulfate (aps) reductase than they do to e. coli cysh. the evidence reported here shows that the cysh from one of the species, pseudomonas aeruginosa, encodes ... | 2000 | 10613872 |
| the replicator of the nopaline-type ti plasmid ptic58 is a member of the repabc family and is influenced by the trar-dependent quorum-sensing regulatory system. | the replicator (rep) of the nopaline-type ti plasmid ptic58 is located adjacent to the trb operon of this conjugal element. previous genetic studies of this region (d. r. gallie, m. hagiya, and c. i. kado, j. bacteriol. 161:1034-1041, 1985) identified functions involved in partitioning, origin of replication and incompatibility, and copy number control. in this study, we determined the nucleotide sequence of a 6,146-bp segment that encompasses the rep locus of ptic58. the region contained four f ... | 2000 | 10613878 |
| characterization of two inducible phosphate transport systems in rhizobium tropici. | rhizobium tropici forms nitrogen-fixing nodules on the roots of the common bean (phaseolus vulgaris). like other legume-rhizobium symbioses, the bean-r. tropici association is sensitive to the availability of phosphate (p(i)). to better understand phosphorus movement between the bacteroid and the host plant, p(i) transport was characterized in r. tropici. we observed two p(i) transport systems, a high-affinity system and a low-affinity system. to facilitate the study of these transport systems, ... | 2000 | 10618197 |
| a new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine: phylogenetic, physiological, and preliminary biochemical studies. | a previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the northern territory of australia. the organism, designated nt-26, was found to be a gram-negative motile rod with two subterminal flagella. in a minimal medium containing only arsenite as the electron donor (5 mm), oxygen as the electron acceptor, and carbon dioxide-bicarbonate as the carbon source, the doubling time for chemolithoautotrophic growth was 7.6 h. arsenite oxidation was f ... | 2000 | 10618208 |
| induction of a futile embden-meyerhof-parnas pathway in deinococcus radiodurans by mn: possible role of the pentose phosphate pathway in cell survival. | statistical models were used to predict the effects of tryptone, glucose, yeast extract (tgy) and mn on biomass formation of the highly radioresistant bacterium deinococcus radiodurans. results suggested that glucose had marginal effect on biomass buildup, but mn was a significant factor for biomass formation. mn also facilitated glucose interactions with other nutrient components. these predictions were verified by in vivo and in vitro experiments. tgy-grown cells metabolized glucose solely by ... | 2000 | 10618210 |
| detection and characterization of plasmid pjp4 transfer to indigenous soil bacteria. | prior to gene transfer experiments performed with nonsterile soil, plasmid pjp4 was introduced into a donor microorganism, escherichia coli atcc 15224, by plate mating with ralstonia eutropha jmp134. genes on this plasmid encode mercury resistance and partial 2, 4-dichlorophenoxyacetic acid (2,4-d) degradation. the e. coli donor lacks the chromosomal genes necessary for mineralization of 2,4-d, and this fact allows presumptive transconjugants obtained in gene transfer studies to be selected by p ... | 2000 | 10618238 |
| transcriptional organization and regulation of a polycistronic cold shock operon in sinorhizobium meliloti rm1021 encoding homologs of the escherichia coli major cold shock gene cspa and ribosomal protein gene rpsu. | a homolog of the major eubacterial cold shock gene cspa was identified in sinorhizobium meliloti rm1021 by luxab reporter transposon mutagenesis. here we further characterize the organization and regulation of this locus. dna sequence analysis indicated that the locus includes three open reading frames (orfs) encoding homologs corresponding to cspa, a novel 10.6-kda polypeptide designated orf2, and a homolog of the escherichia coli ribosomal protein s21. transcription analysis indicated that thi ... | 2000 | 10618253 |
| identification of cold shock gene loci in sinorhizobium meliloti by using a luxab reporter transposon. | using a luxab reporter transposon, seven mutants of sinorhizobium meliloti were identified as containing insertions in four cold shock loci. luxab activity was strongly induced (25- to 160-fold) after a temperature shift from 30 to 15 degrees c. the transposon and flanking host dna from each mutant was cloned, and the nucleic acid sequence of the insertion site was determined. unexpectedly, five of the seven luxab mutants contained transposon insertions in the 16s and 23s rrna genes of two of th ... | 2000 | 10618254 |
| the pspa protein of escherichia coli is a negative regulator of sigma(54)-dependent transcription. | in eubacteria, expression of genes transcribed by an rna polymerase holoenzyme containing the alternate sigma factor sigma(54) is positively regulated by proteins belonging to the family of enhancer-binding proteins (ebps). these proteins bind to upstream activation sequences and are required for the initiation of transcription at the sigma(54)-dependent promoters. they are typically inactive until modified in their n-terminal regulatory domain either by specific phosphorylation or by the bindin ... | 2000 | 10629175 |
| regulation of stalk elongation by phosphate in caulobacter crescentus. | in caulobacter crescentus, stalk biosynthesis is regulated by cell cycle cues and by extracellular phosphate concentration. phosphate-starved cells undergo dramatic stalk elongation to produce stalks as much as 30 times as long as those of cells growing in phosphate-rich medium. to identify genes involved in the control of stalk elongation, transposon mutants were isolated that exhibited a long-stalk phenotype irrespective of extracellular phosphate concentration. the disrupted genes were identi ... | 2000 | 10629178 |
| proteolysis of the mcpa chemoreceptor does not require the caulobacter major chemotaxis operon. | the degradation of the mcpa chemoreceptor in caulobacter crescentus accompanies the swarmer cell to the stalked-cell differentiation event. to further analyze the requirements for its degradation, we have constructed a series of strains that have deletions in the mcpa gene and in the mcpa chemotaxis operon. internal deletions of the mcpa gene demonstrate that the highly conserved domain (signalling unit) and the methylation domains are not required for cell cycle-regulated proteolysis. the delet ... | 2000 | 10629199 |
| the amino terminus of salmonella enterica serovar typhimurium sigma(54) is required for interactions with an enhancer-binding protein and binding to fork junction dna. | transcription initiation by the sigma(54)-rna polymerase holoenzyme requires an enhancer-binding protein that is thought to contact sigma(54) to activate transcription. to identify potential enhancer-binding protein contact sites in sigma(54), we compared the abilities of wild-type and truncated forms of salmonella enterica serovar typhimurium sigma(54) to interact with the enhancer-binding protein dctd in a chemical cross-linking assay. removal of two regions in the amino-terminal portion of si ... | 2000 | 10629201 |
| environmental regulation of exopolysaccharide production in sinorhizobium meliloti. | exopolysaccharide production by sinorhizobium meliloti is required for invasion of root nodules on alfalfa and successful establishment of a nitrogen-fixing symbiosis between the two partners. s. meliloti wild-type strain rm1021 requires production of either succinoglycan, a polymer of repeating octasaccharide subunits, or eps ii, an exopolysaccharide of repeating dimer subunits. the reason for the production of two functional exopolysaccharides is not clear. earlier reports suggested that low-p ... | 2000 | 10633091 |
| discovery of a nonclassical siderophore, legiobactin, produced by strains of legionella pneumophila. | the mechanisms by which legionella pneumophila, a facultative intracellular parasite and the agent of legionnaires' disease, acquires iron are largely unexplained. several earlier studies indicated that l. pneumophila does not elaborate siderophores. however, we now present evidence that supernatants from l. pneumophila cultures can contain a nonproteinaceous, high-affinity iron chelator. more specifically, when aerobically grown in a low-iron, chemically defined medium (cdm), l. pneumophila sec ... | 2000 | 10633110 |
| visn and visr are global regulators of chemotaxis, flagellar, and motility genes in sinorhizobium (rhizobium) meliloti. | the known 41 flagellar, chemotaxis, and motility genes of sinorhizobium (rhizobium) meliloti contained in the "flagellar regulon" are organized as seven operons and six transcription units that map to a contiguous 45-kb chromosomal region. by probing gene expression on western blots and with lacz fusions, we have identified two master regulatory genes, visn and visr, contained in one operon. the gene products probably form a heterodimer, visnr, acting as a global transcription activator of other ... | 2000 | 10633114 |
| isolation of neisseria gonorrhoeae mutants that show enhanced trafficking across polarized t84 epithelial monolayers. | initiation of a gonococcal infection involves attachment of neisseria gonorrhoeae to the plasma membrane of an epithelial cell in the mucosal epithelium and its internalization, transepithelial trafficking, and exocytosis from the basal membrane. piliation and expression of certain opa proteins and the immunoglobulin a1 protease influence the transcytosis process. we are interested in identifying other genetic determinants of n. gonorrhoeae that play a role in transcellular trafficking. using po ... | 2000 | 10639460 |
| conformational changes induced by phosphorylation of the fixj receiver domain. | a variety of bacterial adaptative cellular responses to environmental stimuli are mediated by two-component signal transduction pathways. in these phosphorelay cascades, histidine kinases transphosphorylate a conserved aspartate in the receiver domain, a conserved module in the response regulator superfamily. the main effect of this phosphorylation is to alter the conformation of the response regulator in order to modulate its biological function. the response regulator fixj displays a typical m ... | 1999 | 10647181 |
| structural transitions in the fixj receiver domain. | two-component signal transduction pathways are sophisticated phosphorelay cascades widespread in prokaryotes and also found in fungi, molds and plants. fixl/fixj is a prototypical system responsible for the regulation of nitrogen fixation in the symbiotic bacterium sinorhizobium meliloti. in microaerobic conditions the membrane-bound kinase fixl uses atp to transphosphorylate a histidine residue, and the response regulator fixj transfers the phosphoryl group from the phosphohistidine to one of i ... | 1999 | 10647182 |
| function of a principal na(+)/h(+) antiporter, shaa, is required for initiation of sporulation in bacillus subtilis. | shaa (sodium/hydrogen antiporter, previously termed yuft [or ntra]), which is responsible for na(+)/h(+) antiporter activity, is considered to be the major na(+) excretion system in bacillus subtilis. we found that a shaa-disrupted mutant of b. subtilis shows impaired sporulation but normal vegetative growth when the external na(+) concentration was increased in a low range. in the shaa mutant, sigma(h)-dependent expression of spo0a (p(s)) and spovg at an early stage of sporulation was sensitive ... | 2000 | 10648512 |
| prpr, ntra, and ihf functions are required for expression of the prpbcde operon, encoding enzymes that catabolize propionate in salmonella enterica serovar typhimurium lt2. | the genes required for the catabolism of propionate in salmonella enterica serovar typhimurium are organized as two transcriptional units (prpr and prpbcde) that are divergently transcribed from one another. sequence homology to genes encoding members of the sigma-54 family of transcriptional activators and the identification of a consensus sigma-54 promoter 5' to the prpbcde operon suggested that prpr was required to activate expression of this operon. we isolated insertions in prpr and showed ... | 2000 | 10648513 |
| mutagenesis and functional characterization of the glnb, glna, and nifa genes from the photosynthetic bacterium rhodospirillum rubrum. | nitrogen fixation is tightly regulated in rhodospirillum rubrum at two different levels: transcriptional regulation of nif expression and posttranslational regulation of dinitrogenase reductase by reversible adp-ribosylation catalyzed by the drat-drag (dinitrogenase reductase adp-ribosyltransferase-dinitrogenase reductase-activating glycohydrolase) system. we report here the characterization of glnb, glna, and nifa mutants and studies of their relationship to the regulation of nitrogen fixation. ... | 2000 | 10648524 |
| high-resolution physical map of the sinorhizobium meliloti 1021 psyma megaplasmid. | to facilitate sequencing of the sinorhizobium meliloti 1021 psyma megaplasmid, a high-resolution map was constructed by ordering 113 overlapping bacterial artificial chromosome clones with 192 markers. the 157 anonymous sequence tagged site markers (81,072 bases) reveal hypothetical functions encoded by the replicon. | 2000 | 10648551 |
| dna sequence analysis of the photosynthesis region of rhodobacter sphaeroides 2.4.1. | this paper describes the dna sequence of the photosynthesis region of rhodobacter sphaeroides 2.4.1 (t). the photosynthesis gene cluster is located within a approximately 73 kb ase i genomic dna fragment containing the puf, puha, cyca and puc operons. a total of 65 open reading frames (orfs) have been identified, of which 61 showed significant similarity to genes/proteins of other organisms while only four did not reveal any significant sequence similarity to any gene/protein sequences in the da ... | 2000 | 10648776 |
| glycine betaine, carnitine, and choline enhance salinity tolerance and prevent the accumulation of sodium to a level inhibiting growth of tetragenococcus halophila. | natural-abundance (13)c-nuclear magnetic resonance was used to probe the intracellular organic solute content of the moderately halophilic bacterium tetragenococcus halophila. when grown in complex growth media supplemented or not with nacl, t. halophila accumulates glycine betaine and carnitine. unlike other moderate halophiles, t. halophila was not able to produce potent osmoprotectants (such as ectoines and glycine betaine) through de novo synthesis when cultured in defined medium under hyper ... | 2000 | 10653711 |
| cytochrome c(3) mutants of desulfovibrio desulfuricans. | to explore the physiological role of tetraheme cytochrome c(3) in the sulfate-reducing bacterium desulfovibrio desulfuricans g20, the gene encoding the preapoprotein was cloned, sequenced, and mutated by plasmid insertion. the physical analysis of the dna from the strain carrying the integrated plasmid showed that the insertion was successful. the growth rate of the mutant on lactate with sulfate was comparable to that of the wild type; however, mutant cultures did not achieve the same cell dens ... | 2000 | 10653734 |
| immunolocalization of dinitrogenase reductase produced by klebsiella pneumoniae in association with zea mays l. | the endophytic lifestyle of klebsiella pneumoniae is described, including the production of dinitrogenase reductase by bacteria residing in maize root tissue. the green fluorescent protein (gfp) was used to detect the colonization of maize by k. pneumoniae strains 2028 and 342. these strains were found to reside in intercortical layers of the stem and within the region of maturation in the root. the production of dinitrogenase reductase by gfp-tagged bacteria was visualized using immunolocalizat ... | 2000 | 10653751 |
| analysis of medicago truncatula nodule expressed sequence tags. | systematic sequencing of expressed sequence tags (ests) can give a global picture of the assembly of genes involved in the development and function of organs. indeterminate nodules representing different stages of the developmental program are especially suited to the study of organogenesis. with the vector lambdahybrizap, a cdna library was constructed from emerging nodules of medicago truncatula induced by sinorhizobium meliloti. the 5' ends of 389 cdna clones were sequenced, then these ests w ... | 2000 | 10656586 |
| n-deacetylation of sinorhizobium meliloti nod factors increases their stability in the medicago sativa rhizosphere and decreases their biological activity. | nod factors excreted by rhizobia are signal molecules that consist of a chitin oligomer backbone linked with a fatty acid at the nonreducing end. modifications of the nod factor structures influence their stability in the rhizosphere and their biological activity. to test the function of n-acetyl groups in nod factors, nodsm-iv(c16:2,s) from sinorhizobium meliloti was enzymatically n-deacetylated in vitro with purified chitin deacetylase from colletotrichum lindemuthianum. a family of partially ... | 2000 | 10656587 |
| expression profiles of 22 novel molecular markers for organogenetic pathways acting in alfalfa nodule development. | during symbiotic nodule development, a variety of molecular signals of rhizobia and plant origin are likely to be involved in the control of the expression of specific genes in the legume medicago sativa (alfalfa). twenty-two new, nodule-associated expressed sequence tags (ests, msnod clones) as well as 16 clones for previously reported alfalfa nodulins were identified by cold-plaque screening. protein homologs were found for 10 of the 22 msnod-encoded polypeptides, revealing putative novel func ... | 2000 | 10656590 |
| mucr is necessary for galactoglucan production in sinorhizobium meliloti efb1. | sinorhizobium meliloti can produce two types of acidic exopolysaccharides, succinoglycan and galactoglucan, that are interchangeable for infection of alfalfa nodules. strain su47 and derivatives produce only succinoglycan, unless it grows under phosphate limitation or carries a mutation in either of two regulatory loci, mucr or expr. it has been proposed that mucr acts as a transcriptional repressor that blocks the expression of the exp genes responsible for galactoglucan production. strain efb1 ... | 2000 | 10656595 |